Things out my liverock?

I have had my tank now for about 16 mos. I have notice long, flat yet has hairy tenticals on the tips, They wave in the current. I have used Joes Juice to try and get rid of some. I put it in the middle to kill/get rid of them. At the same time Is there a way to clean the live rock?
Also, I've notice a blackish film about every 2/3 days on the sands. I syphon it off when I do a weekly 5 gal. water change. What could this be and how can I get rid of it? I have 3 powerheads in different directions.
My tank is a 90 gal. with a 55 gal. (half full) for the refugium. I have fish, mushroom, Kenya in the tank. I keep the tank at about 79 to 80 degrees. I have a fan on for high temps.
Can anyone help me?
DC

 

peppermint shrimp work best if you think it is aiptasia. as for the film on the sand, sounds like your param. are out of wack and not enough flow. What size are your powerheads and what kind of return pump do you have.

 

I did have a shrimp in the tank about 6 mos ago, but lost him.
My powerheads are: (1) Powersweep 226 (2) Maxi-Jet 600 (1) Koralia 1 that I just bought today.
My return is a over the side return that goes down into my refugium.

 

I don't know about the powersweep, but the maxi jet 600 and koralia 1 seem a little on the weak side. I have a 55 and have a total of 1700 gph from my powerheads, two maxi jet 1200, 1 with a mod for 1200gph, and 1 koralia 1, plus my filter and skimmer. Now to your problem, it could be cyno, I had a case of that and it grew on my sand in a sheet. real ugly looking. You can try to increase flow, change bulbs if they are old, keep alkalinity up and suck out as much as possible.

 

They could be mini feather dusters, another common hitch hiker. The black slime is a type of cyanobacteria. Usually means you're leaving your lights on too long.

 

So you have Powersweep 226 = 196GPH, 2xMJ = 380GPH, K-1 = 400GPH and your return at probably 400GPH. That's about 1400GPH rounded up.

For a 90g tank I would have at least 30 to 40x turnover which is 2700 to 3600GPH. I am running 2600GPH in my 75g and am going to add more. So, for you and you cyano problem, I would do upwards of 40x and aim for around 3600GPH.

I would buy two Koralia 4s at 1200GPH each. One on each side. You could position the K-1 in the back. I would also buy a Koralia 2 to replace the MJ600s and the PS226. Buy one and get rid of three. It would clean things up a bit.

The Koralias, and the return would then give you a total of about 3800GPH flow. Thats about 42x turnover.

So, that's what I would do with the flow situation. JMO.